Lance for metal refining



Aprl 22, 1969 J. H. BARNARD ETAL LANCE FOR METAL REFINING Sheet Fired April 2o, 1964 @NNW Mh.

April 22, 1969 J. H. BARNARD ETAL. 3,439,911

LANCE FOR METAL REFINING Sheet Filed April 20, 1964 IIY NNNY

Sheeil J. H. BARNARD ETAL LANCE FOR METAL REFINING T132 I lv April z2, 1969 Filed April 20, 1964 /AU//M J April 22, 1969 J. H. BARNARD ETAL 3,439,911

LANCE FOR METAL REFINING Sheet Filed April 20, 1964 Il IJ April 22, 1969 J. H. BARNARD ETAL 3,439,911

LANCE FOR METAL REFINING Filed April 2o, 1964 sheet 5 of 5 United States Patent O 3,439,911 LANCE FOR METAL REFINING Jan Hendrik Barnard, Muckleneuk, Pretoria, Transvaal,

and Dick Toet, Hazelwood, Pretoria, Transvaal, Republic of South Africa, assignors to South African Iron and Steel Industrial Corporation Limited Filed Apr. 20, 1964, Ser. No. 360,899 Claims priority, application Republic of South Africa, Apr. 26, 1963, 63/1,808 Int. Cl. C21c 5/42, 5/44 U.S. Cl. 266-34 17 Claims ABSTRACT F THE DISCLOSURE This invention relates to metal refining and particularly to apparatus for refining metal.

Oxygen steelmaking in which refining oxygen is introduced at an acute angle through a lance to a bath of molten metal to be refined, is well known. It is normal practice for a lance to be held stationary during a heat and it has been found with conventional stationary lances that localized heating in the region of the resulting stationary reaction zone causes erosion of the refractory lining of the refining vessel containing the bath of molten metal, as a result of excessive heating of the refractory lining above the reaction zone, as well as by scouring of the lining immediately below the reaction zone by the rapid flow of molten metal caused by heating in the reaction zone. Localized erosion occurs which limits the life of the refractory lining.

In order to spread the erosion over a greater portion of the lining, it has been suggested to use a series of stationary lances of different lengths for a sequence of heats, the lance length increasing progressively as the sequence of heats progresses. During each heat, the lance in use is held stationary so that the reaction zone will be stationary during each heat, but as the sequence of heats progresses, the reaction zone is moved progressively along the bath.

Although this arrangement decreases lining wear, such wear is still great since the temperature of the refractory lining above each reaction zone rises to an excessive value. Also, time is wasted in fitting to the lance carriage new lances of different length during a sequence of heats. Furthermore, substantial Vibrational effects are to be expected when the lance length increases.

It is an object of the present invention to provide an improved lance suitable for use in refining metal, at least certain forms of the lance of the invention being capable of minimizing the above disadvantages. It is a further object of the invention to provide an improved method of oxygen steelmaking or other refining of iron.

According to the invention there is provided a lance which has a root and a tip at opposite ends and is arranged to be mounted in cantilever fashion at its root, the lance including a hollow carrier beam extending from the root towards the tip; a jacket for cooling medium surrounding the carrier beam; and at least one discharge nozzle at the tip of the lance for material conveyed to the tip within the carrier beam.

The hollow carrier beam may be adapted lby itself to convey material to the discharge nozzle, but preferice ably the lance includes a material supply conduit located within the carrier beam and connected to the discharge nozzle.

The cooling medium jacket may be divided into two separate longitudinally extending sections arranged respectively to convey cooling medium to the lance tip and to return cooling medium from the lance tip.

Preferably, the jacket is divided into a longitudinal extending upper section for conveying cooling medium to the lance tip, and a longitudinally extending lower section for returning cooling medium from the lance tip.

The lance may taper longitudinally from its root towards its tip to reduce stress at the root of the lance.

The carrier beam may be constituted by upper and lower longitudinally extending sections which are frictionally associated with each other for the damping of vibration. The two sections may be arranged to provide slip damping at friction interfaces disposed substantially parallel to the neutral axis of the lance.

In order to increase the frictional effect, a friction member may be interposed between friction surfaces presented by the upper and lower sections of the carrier beam, thereby to provide double interface slip damping.

Alternatively or additionally, the carrier beam may be rnade of spheroidal graphitic cast iron having high damping qualities, in order to minimize vibration.

Thelance may be mounted so as to be capable of pivotal movement about a substantially horizontal transverse axis to permit adjustment of the vertical disposition 0f the lance tip.

The lance may be mounted for longitudinal reciprocating movement.

The lance may be arranged to extend substantially horizontally into a metal rening vessel and to be located above the surface of a bath of molten metal in the rening vessel, the discharge nozzle being arranged to direct refining medium downwardly towards the bath surface.

The mouth of the discharge nozzle may be arranged to be located above, at or below the bath surface, as required.

The lance may further include at least one auxiliary nozzle for discharging material into the refining vessel in the space above the metal bath; and a supply conduit for the auxiliary nozzle located within the carrier beam.

The lance may be mounted on a carriage arranged to Ibe located outside the refining vessel and to move to yand fro longitudinally with respect to the lance with the ylatter extending into the relining vessel through a mouth thereof.

The carriage may include at least two vertically spaced sets of wheels arranged to engage two sets of vertically spaced rails, the one set of wheels being located towards the end of the carriage from which the lance projects and arranged to engage on top of the one set of rails, the other set of wheels being located towards the opposite end of the carriage and arranged -to engage underneath the other set of rails.

The lance may include a downwardly directed tip and each set of rails may `include a substantially horizontal main section adjacent the refining vessel along which the carriage can move rto reciprocate the lance, 4and a downwardly sloping end section remote from the relining vessel along which the carriage can move to tilt the lance for withdrawal and insertion of the lance tip through `the mouth of the reiining vessel.

Each wheel on one side of the carriage may include a pair of spaced anges arranged for location on opposite `sides of the associated rail, and all the wheels on the opposite side of lthe carriage lmay be in the form of unanged rollers.

Biassing means may be provided for urging at least one set of wheels into engagement with their associated rails, thereby to increase frictional engagement between the wheels of the carriage and the rails.

According to another aspect of the invention a method of steelmaking or other refining of iron includes the steps of providing a bath of molten metal to be refined; introducing refining medium to the bath; imparting a circulatory motion about an axis to `the metal of the bath; and causing the zone of introduction of the refining medium to move relative `to the bath at least in a longitudinal direction with respect lto -the axis of circulatory motion of the metal.

The circulatory motion about the axisl may be imparted to the metal of the bath by rotation of the vessel about that axis, and refining medium may be introduced through a reciprocating lance as defined above, the lance reciprocating longitudinally with respect to the axis of circulatory motion of 'the metal bath.

It is to be noted that for the purposes of this specification the term reciprocating lance is intended to include not only a lance which is actually reciprocating, but any lance capable of, or adapted for reciprocating movement.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a side elevational view showing the general arrangement of a reciprocating lance according to the invention suitable for oxygen steelmaking.

=FIGURE 2 is a sectional elevational view of the tip of the lance of FIGURE il.

FIGURE 3 is a section on the line III- III in FIG- URE 2.

FIGURE 4 is a section on the line IV--IV in FIG- URE 2.

FIGURE 5 is a sectional elevational view to a reduced scale relative to FIGURES 2 to 4, of the root ofthe lance of FIGURE 1.

FIGURE 6 is a section on line VI-VI in FIGURE 5.

FIGURE 7 is a side elevational view of the lance carriage and lance clamping means of FIGURE l.

FIGURE 8 is a partly sectioned end elevational view from the front, of the lance carriage and lance clamping means of FIGURE 1i FIGURE 9 is a partly sectioned end elevational view from the rear, of the lance carriage and lance clamping means of FIGURE l.

Referring to FIGURE 1, lance 1 is suspended at its root end 1a and in cantilever fashion from rail carriage 2 which is located outside refining vessel 3 and is mounted on rails 4, 53. Lance 1 is held at its root end 1a by clamping means 8.

In its operative position (indicated in solid outline) lance 1 is disposed substantially horizontally within refining vessel 3 above the surface of a bath 5 of -molten metal within refining vessel 3. Lance 1 has a downwardly directed tip 6 through which oxygen or other refining medium may be discharged downwardly onto or into metal lbath 5. Lance 1 is further provided at tip 6 with a downwardly directed auxiliary nozzle 7 for discharging any required material, such as secondary oxygen and/or fiuxes and/or ore, into the space above metal bath 5.

`By moving carriage 2 to and fro along rails 4, 53, -as will be described in greater detail hereinafter, lance 1 can be reciprocated within refining vessel 2 in a substantially horizontal direction as indicated by arrows A.

Clamping means 8 is mounted on carriage 2 by means of pin 9 for pivotal movement about a transverse horizontal axis relative to carriage 2. Lance 1 can be pivoted on pin 9 by means of hydraulic ram 10 to lthe rear of clamp means 8, thereby to permit adjustment of the vertical disposition of lance tip 6 as indicated by arrows B.

As shown in dotted outline in FIGURE 1 and as will be described in greater detail hereinafter, lance 1 can be withdrawn completely from refining vessel 3.

By using reciprocating lance 1 for oxygen steel-making or other refining of iron, the zone of introduction of refining oxygen to metal bath 5 in refining vessel 3, can be moved relative to metal bath 5. Erosion of refractory lining 11 of vessel 3 can thus be spread more or less evenly over a large part of the lining, and localized wear can be minimized. This greatly extends lining life.

Also, by reciprocating lance 1 to move the zone of introduction by refining oxygen relative to metal -bath 5, the metal body is subjected more uniformly to the action of the refining medium. This has a two-fold advantage. Firstly, the final product is more 4uniform in composition. Secondly, the gradient of unrefined metal, i.e., the amount of unrefined metal in the reaction zone divided by the amount of refining medium suppliedin the reaction zone, is greater with a moving reaction zone since localized over-refinement is prevented. This results in greater oxygen utilization efficiency, a saving in time and also eliminates the tendency to burn iron during the major period of the heat since carbon is more readily available for combustion.

Reciprocating lance 1 can be made to penetrate deeply into refining vessel 3 and it is contemplated that solid and/or gaseous material may be introduced into vessel 3 and directed as required by means of auxiliary nozzle 7. For example, ore and/or fluxes or oxygen, air enriched in oxygen, air or steam or the like may be directed at the reaction zone.

With horizontal rotary converters, which are well known for steelmaking, it is normal practice to blow oxygen through a stationary lance from one end of the vessel while rotating the vessel about its longitudinal axis, and then to reverse the position of the vessel by slewing it about a transverse axis to permit oxygen blowing through the same lance from the other end of the vessel. This reversal in position of the vessel is time consuming and can be eliminated altogether by using a reciprocating lance.

Considering various aspects of the lance arrangement of FIGURE l in greater detail, it will be seen from FIG- URES 2 to 6 that lance 1 includes a hollow carrier beam 12 extending longitudinally along lance 1 from its root 1a. to its tip 6. Carrier beam 12 is constituted -by two elongated members 13 of top hat section which extend longitudinally along lance 1 and are secured together with their cavities 14 facing each other, by means of securing bolts, such as 15 in FIGURE 6, passing through fianges 13a of top hat sections 13.

The two elongated top hat sections 13 are separated by partition plate 16 which extends on opposite sides 16a beyond flanges 13a of top hat sections 13, and which is slotted to pass the securing bolts 15.

Partition plate 16 constitutes a friction member interposed between friction surfaces presented yby the opposed faces of flanges 13a of top hat sections 13. Double interface slip damping due to frictional engagement between flanges 13a and partition plate 16 will serve to damp high amplitude vibrations in carrier beam 12. The friction interfaces are disposed substantially parallel to the neutral axis of lance 1.

In order further to minimize vibration, top hat sections 13 constituting carrier beam 12 are made of spheroidal graphitic cast iron having high damping qualities.

Cooling jacket 18 is made of steel and surrounds carrier beam 12 and is divided by projecting ends 16a of partition plate 16 into longitudinally extending upper and lower sections constituting upper cooling medium passage 19 and lower cooling medium passage 20. Upper cooling medium passage 19 communicates with chamber 21 which has an inlet 21a (FIGURE 5) which is connected to iiexible tube 22 (FIGURE 1). Lower cooling medium passage 20 communicates with chamber 23 which has an outlet 23a (FIGURE 5) which is connected to fiexible tube 24 (see FIGURE 1).

Projecting ends 16a of partition plate 16 are secured to jacket 18, for example, by welding. Jacket 18 is further located relative to carrier beam 12 by means of spacers 17 (FIGURE 3).

As can be seen from FIGURES 2 and 4, lance tip 6 comprises outer tube 30 housing discharge tube 28 provided with main discharge nozzle 28a. Partition plate 16 of lance 1 is connected to division plates 31 in lance tip 6. Division plates 31 divide the annular passage between outer tube 30 and discharge tube 28 into upper section 19a which communicates with upper passage 19 located around carrier beam 12, and lower section 20a. which communicates with lower passage 20 located around carrier beam 12. The lower ends 31a of division plates 31 stop short of the lower end of lance tip 6 to provide communication between upper and lower passage sections 19a and 20a.

Cooling medium supplied by tube 22 to chamber 21, passes along upper passage 19 to lance tip 6, passes along upper passage section 19a. to lower passage section 20a in tip 6, and returns along lower passage 20 from tip 6 to chamber 23 for withdrawal through tube 24.

Carrier beam 12 houses two conduits 25, 26. Main conduit 2S is located below partition plate 16, is connected at one end at the root of lance 1 to flexible tube 27 (see FIGURE 1), and is connected at the other end with downwardly directed discharge tube 28 in lance tip 6. Auxiliary conduit 26 is located above partition plate 16, is connected at one end at the root of lance 1 to iiexible tube 29 (see FIGURE 1), and is connected at the other end to auxiliary nozzle 7 at lance tip 6.

Rening medium, such as primary oxygen, can Ibe supplied from tube 27 to main conduit 25 for discharge through main nozzle 28a in tip 6. By suitably controlling the discharge velocity of the refining medium from main nozzle 28a, the rening medium can either be blown onto the surface of metal bath 5 without any appreciable penetration, or blown to penetrate into the metal of bath 5 as may be required. The mouth of discharge nozzle 28a may be located above, at or below the surface of bath 5, as required.

Any suitable material such as secondary oxygen and/0r iluxes and/ or ore, can be supplied from tube 29 to auxiliary conduit 26 for discharge through auxiliary nozzle 7 into refining vessel 3 in the space above the level of metal bath 5.

Flexible tubes 22, 24, 27, 29 permit reciprocation of lance 1 as can be seen from FIGURE 1.

Carrier beam 12 tapers from the root to the tip of lance 1 in elevational view as well as in plan view. Cooling jacket 18 tapers similarly so that lance 1 as a whole tapers from root to tip when viewed in elevation as shown in FIGURE l, as well as in plan view (not shown). The taper reduces stress at the root end 1a of lance 1. The cross-section of jacket 1S may change along the length of lance 1 as can be seen from FIGURES 3 and 6.

By using a hollow `carrier beam 12 surrounded by a cooling medium jacket 1S divided into longitudinally extending passages 19, 2t), a strong compact structure can be obtained having a minimum of weight and cros's-sectional dimensions for the required resistance against bending, at the same time providing good cooling. Also, by dividing cooling jacket 18 into upper and lower passages 19, 20 as described above, cooling medium travelling along upper passage 19 to lance tip 6 might be expected to be at a lower temperature than cooling medium returning frorn the tip 6 along the lower passage 20. The relative expansion between the upper and lower sections of the lance as a result of this temperature difference will tend to lift lance tip 6.

The construction of lance 1 as described above permits cooling jacket 18 to be made of steel which is cheaper and easier to work than copper from which cooling jackets for lances have generally been made hitherto.

FIGURES 7 and 8 show clamping means 8 which comprises jaws 32 embracing root end 1a` of lance 1. Each jaw 32 is provided with four pairs of ribs 33, a pivot pin 34 carrying a link 35a or 351) being secured between each pair ot ribs 33. At its lower end, each link 35a pivotally carries a pair of clamping plates 36. At its lower end, each link 35b is arranged detachably to engage a pair of clamping plates 36.

Pressure plate 37 extends longitudinally relative to lance 1 and is provided with four depending tongues, such as 38 in FIGURE 8. Each tongue 38 is pivotally connected between its own pair of clamping plates 36 by means of a pin 39. This permits pivotal movement of pressure plate 37 about a horizontal axis common to all four pins 39 and extending longitudinally relative to lance 1.

Upper and lower surfaces 49a, 4% at root end 1a of lance 1 are clamped in a vertical direction between pressure plate 37 and pressure surface 41 located between jaws 32. The clamping pressure can be adjusted by means of nuts 61 on links 3512. Pads 43 are provided on clamp means 8 to locate lance 1 in a horizontal direction.

Clamp means 3 further includes a tail piece 44 extending rearwardly from jaws 32. Tail piece 44 is mounted by means of pin 9 on carriage 2 for pivotal movement rabout a horizontal transverse axis. Hydraulic ram 10 is connected between the rear end of tail piece 44 and carriage 2. By extending and collapsing ram 10, lance 1 can be pivoted for vertical adjustment of lance tip 6 as indicated by arrows B in FIGURE l.

As shown in FIGURES 7, 8 and 9, carriage 2 is provided fore and aft with two pairs of upper wheels 45a, 45b and 46a, 46h engaging upper rails 4, and a pair of lower Wheels 47a, 47b engaging inverted lower rails 53. Upper wheels 45a, 45h and 46a, 46h engage on top of upper rails 4 and lower wheels 47a, 47b engage underneath inverted lower rails 53. Rails 4 and 53 are mounted on stanchions 54.

It has been found that if conventional single anged railway type wheels are used on a carriage with a short wheel base, the lateral forces at tip 6 of lance 1 may subject the carriage to excessive lateral sway. In order to increase transverse stability, each wheel 45a, 46a, 47a on the one side of carriage 2 includes a pair of spaced ilanges 48, for location on opposite sides of the associated rail, and all the wheels 45h, 46h, 47b on the other side of carriage 2 are in the form of unanged rollers.

As will be clear from FIGURES 7 and 9, upper rear wheels 46a, 4617 are mounted on half axles 49a, 49b respectively which are, in turn, pivotally mounted relative to carriage 2 on pin 50 at their inner ends. Towards the outer ends of half axles 49a, 49b resilient pads 51 of rubber or any other suitable material are interposed between carriage 2 and half axles 49a, 4911 thereby resiliently biassing upper rear wheels 46a, 4Gb into engagement with upper rails 4 and increasing frictional engagement between wheels 45a, 45b, 46a, 46h, 47a, 47b and rails 4, S3, thus increasing transverse stability. Set screws 52 and pressure plates S5 are provided for adjusting the biassing force exerted by pads 51.

As can be seen from FIGURE 1, lance 1 has a fairly long downwardly directed tip 6. In order to facilitate insertion and withdrawal of tip 6 through the mouth 3a of refining vessel 3, rails 4, 53 have substantially horizontal main sections 4a, 53a along which carriage 2 moves to and fro to reciprocate lance 1 horizontally within vessel 3 as indicated by arrows A, and outer end portions 4b, 53h sloping downwardly away from vessel 3. By running carriage 2 onto sloping rail end portions 4b, 5311, carriage 2 and lance 1 are tilted suitably, as indicated in dotted outline in FIGURE 1, to permit withdrawal and insertion of lance tip 6 through vessel mouth 3a.

With certain refining vessels it might not be necessary to tilt lance 1 to withdraw and insert tip 6 through the mouth of the refining vessel, in which case rails 4, 53 may be horizontal throughout their length.

Carriage 2 can be propelled to and fro along rails 4, 53 by means of a reversible fluid motor 56 which is drivingly coupled to wheel 4517 which, in turn, is drivingly coupled to wheel 45a by means of axle 57 which 7 is rotatably mounted in bearings 58, as shown in FIG- URE 8.

As can be seen from FIGURE l, rails 4, 53 are located above vessel mouth 3a. Not only do carriage 2 and rails 4, 53 remain cleaner, but considerable floor space is left clear for personnel movement and other purposes. If required, stationary screen 59 may be provided in front of vessel mouth 3a for protecting equipment adjacent vessel 3. Slot 60 is provided in screen 59 to permit vertical movement of lance 1 as well as withdrawal and insertion of lance tip `6 through vessel mouth 3a.

For high pressure discharge from main nozzle 28a and auxiliary nozzle 7, supply conduits such as 25, 26 are normally essential. However, for certain low pressure discharge applications, it might be possible to dispense with a special supply conduit for at least one of the discharge nozzles, the material to be discharged being conveyed by carrier beam 12 itself within the upper and/or lower innen passage defined bythe walls of carrier beam 12 and partition plate 16.

If required, lance 1 may be provided with one or more suitably located discharge nozzles in addition to main nozzle 28a and auxiliary nozzle 7. A suitable supply conduit for each additional nozzle may be provided within carrier beam 12.

Instead of reciprocating lance 1 during the introduction of refining medium to metal bath 5, lance 1 can be held stationary during the introduction of refining medium. For certain applications, lance 1 may even be mounted in cantilever fashion on a stationary support so that no reciprocation of lance 1 is possible. It may, however, still be mounted so as to be capable of pivotal movement to permit adjustment of the vertical disposition of lance tip 6.

Lance 1 as described above is particularly applicable to oxygen steelmaking, but may also be used for other metal refining processes.

The advantages of -a reciprocating lance 1 for oxygen steelmaking or other refining of iron are described above. Further advantages may be derived by imparting a circulatory motion about an axis, to the molten metal of bath at the same time as refining medium is introduced to bath 5 through main nozzle 28a of lance 1 during reciprocating movement of lance 1, so that the zone of introduction of refining medium moves relative to bath 5 in a longitudinal direction with respect to the axis of circulatory motion of the metal of bath 5.

The required circulatory motion may be imparted to the metal of bath 5 by rotating refining Vessel 3 about its horizontal longitudinal axis XX as indicated by arrow C, in FIGURE 1.

It is also contemplated that vessel 3 may be nonrotary and that the required circulatory motion may be mparted to the metal of bath 5 in any suitable manner, such as by electromagnetic stirring.

Apart from being directed downwardly, lance tip 6 may also extend at an angle transversely from lance 1 when viewed in plan. The transverse angle of tip 6 and the velocity of discharge of refining medium from nozzle 28a may be arranged to impart or assist in imparting the required circulatory motion to the metal of bath 5. The circulatory motion may be aided by the specific shape of the hearth containing metal bath 5.

Apart from reciprocating longitudinally relative to the axis of circulatory motion, lance 1 may also be arranged for tip 6 to have a horizontal component of movement transversely to the circulatory axis.

We claim:

1. A lance having a root and a tip at opposite ends and mountable in cantilever fashion at its root; the lance including a hollow carrier beam extending from the root towards the tip, the carrier beam being constituted by upper and lower longitudinally extending section which are frictionally associated with each other for the damping of vibrations; a jacket for cooling medium surrounding the carrier beam; and at least one discharge nozzle at the tip of the lance for material conveyed to the tip within the carrier beam.

2. A lance as claimed in claim 1, including a material supply conduit located within the carrier beam and connected to the discharge nozzle.

3. A lance as claimed in claim 1, in which the cooling medium jacket is divided into two separate longitudinally extending sections arranged respectively to convey cooling medium to the lance tip and to return cooling medium from the lance tip.

4. A lance as claimed in claim 1, which tapers longitudinally from its root towards its tip.

5. A lance as claimed in claim 1, in which the carrier beam is made of spheroidal graphitic cast iron.

6. A lance as claimed in claim 1, mounted for pivotal movement about a substantially horizontal transverse axis to permit adjustment of the vertical disposition of the lance tip.

7. A lance as claimed in claim 1, mounted for longitudinal reciprocating movement.

l8. A lance as claimed in claim 1, arranged to extend substantially horizontally into a metal refining vessel and to be located above the surface of a bath of molten metal in the refining vessel, the discharge nozzle being arranged to direct refining medium downwardly towards the bath surface.

9. A lance as claimed in claim 1, in which the jacket is divided into a longitudinally extending upper section for conveying cooling medium to the lance tip, and a longitudinally extending lower section for returning cooling medium from the lance tip.

10. A lance as claimed in claim 1, in which slip damping is provided at friction interfaces disposed substantially parallel to the neutral axis of the lance.

11. A lance as claimed in claim 8, including at least one auxiliary nozzle for discharging material into the refining vessel in the space above the metal bath; and a supply conduit for the auxiliary nozzle located within the carrier beam.

12. A lance as claimed in claim 8, in which the lance is mounted on a carriage arranged to be located outside the refining vessel and to move to and fro longitudinally with respect to the lance with the latter extending into the refining vessel through a mouth thereof.

13. A lance as claimed in claim 10, including a friction member interposed between friction surfaces presented by the upper and lower sections of the carrier beam, thereby to provide double interface slip damping.

14. A lance as claimed in claim 12, in which the carriage includes at least two vertically spaced sets of wheels arranged to engage two sets of vertically spaced rails, the one set of wheels being located towards the end of the carriage from which the lance projects and arranged to engage on top of the one set of rails, the other set of wheels being located towards the opposite end of the carriage and arranged to engage underneath the other set of rails.

15. A lance as claimed in claim 14, in which the lance includes a downwardly directed tip and each set of rails includes a substantially horizontal main section adjacent the refining vessel along which the carriage can move to reciprocate the lance, and a downwardly sloping end section remote from the refining vessel along which the carriage can move to tilt the lance for withdrawal and insertion of the lance tip through the mouth of the refining vessel.

16. A lance as claimed in claim 14, in which each wheel on one side of the carriage includes a pair of spaced flanges arranged for location on opposite sides of the associated rail, and all the wheels on the opposite side of the carriage are in the form of unanged rollers.

17. A lance as claimed in claim 14, including biasing means for urging at least one set of wheels into engage- 9 10 ment with their associated rails thereby to increase fric- 3,194,650 7/ 1965 Kurzinski 266-34 X tional engagement between the wheels of the carriage and 3,241,825 3/ 1966 Jilek et a1 266-34.1

the rails.

I. SPENCER OVERHOLSER, Primary Examiner.

5 EUGENE MAR, Assistant Examiner.

References Cited UNITED STATES PATENTS 3,025,047 3/1962 Reinfeld et al. 266-34.2 U.S. C1. X.R. 3,170,977 2/1965 Obenchain 266--342 Z39-132.3 

